Unless otherwise indicated herein, the description in this section is not prior art to the claims and is not admitted to be prior art by inclusion in this section.
A typical wireless communication system includes a number of base stations each radiating to define a respective coverage area in which wireless communication devices (WCDs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped devices, can operate. In turn, each base station may be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a WCD within coverage of the system may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other WCDs served by the base station.
In practice, physical base station equipment in such a system may be configured to provide multiple coverage areas, differentiated from each other by direction, carrier frequency, or the like. For simplicity in this description, however, each coverage area may be considered to correspond with a respective base station and each base station may be considered to correspond with a respective coverage area. Thus, an arrangement where physical base station equipment provides multiple coverage areas could be considered to effectively include multiple base stations, each providing a respective one of those coverage areas.
Further, a wireless communication system may operate in accordance with a particular air interface protocol or “radio access technology,” with communications from the base stations to WCDs defining a downlink or forward link and communications from the WCDs to the base stations defining an uplink or reverse link. Examples of existing air interface protocols include, without limitation, Orthogonal Frequency Division Multiple Access (OFDMA) (e.g., Long Term Evolution (LTE) or Wireless Interoperability for Microwave Access (WiMAX)), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), Global System for Mobile Communications (GSM), and Wi-Fi, among others. Each protocol may define its own procedures for managing communications with WCDs.
In accordance with the air interface protocol, each coverage area may operate on one or more carrier frequencies or ranges of carrier frequencies. Further, each coverage area may define a number of channels or specific resources for carrying signals and information between the base station and WCDs. For instance, on the downlink, certain resources may be used to carry a pilot or reference signal that identifies the coverage area and that WCDs may detect and measure as a basis to evaluate coverage, and other resources may be used to carry paging messages and other such control messages from the base station to WCDs. And on the uplink, certain resources may be used to carry registration requests and other control messages from WCDs to the base station. In addition, certain resources on the uplink and downlink may be set aside to carry bearer traffic (e.g., user communications) between the base station and the WCDs.
When a WCD first powers on or enters into coverage of a wireless communication system, the WCD may search for a strongest coverage area and may then register with the system by transmitting a registration message to the base station that provides that coverage area. The WCD may then operate in an idle mode or a connected (or active) mode in that coverage area. In the idle mode, the WCD may periodically monitor transmissions from the base station in search of any paging messages directed to the WCD and, upon detecting such a paging message or at the initiation of the WCD, may transmit a control message to the base station to facilitate transition to the connected mode. In the connected mode, the WCD may then engage in bearer communication, such as voice calls and/or data sessions, on air interface resources assigned by the base station. Upon completion of the bearer communication, the WCD may transition back into the idle mode.
Further, in both the idle mode and connected mode, the WCD may regularly monitor the strength of its serving coverage area and the strength of any other available coverage areas, to help ensure that the WCD operates in the best available coverage. If the WCD detects that the strength of its serving coverage area is threshold low and the strength of another coverage area is sufficiently high, and/or for other reasons, the WCD may then hand over to operate in the other coverage area. In the connected mode, this handover process would involve signaling between the WCD and the system to facilitate transfer of the WCD's connection to the new coverage area. Whereas, in the idle mode, the handover process may involve the WCD simply transitioning to idle in the new coverage area, beginning to monitor transmissions from the base station in the new coverage area in search of any paging messages directed to the WCD.
In practice, a wireless communication system may include a paging controller, such as a mobile switching center (MSC) or mobility management entity (MME), that manages paging of WCDs. As a WCD may move from coverage area to coverage area, one function of the paging controller is to track where in the wireless communication system the WCD is operating, so that when the paging controller has a paging message to send to the WCD, the paging controller can send the paging message to the appropriate base station(s) for transmission to the WCD. To facilitate this, when a WCD initially registers with the system, the WCD's registration message may pass to the paging controller, and the paging controller may store a record of the base station coverage area currently serving the WCD. Further, as the WCD moves from one coverage area to another in the idle mode, the WCD may re-register with the system by transmitting a new registration message, which may similarly pass to the paging controller, and the paging controller may update its record of which base station coverage area is serving the WCD. When the paging controller then has a page message to send to the WCD, the paging controller may send the paging message to the base station currently serving the WCD for transmission by the base station to the WCD.